diff --git a/src/api/sockets.c b/src/api/sockets.c
index 18f15a21..b3dfdc2f 100644
--- a/src/api/sockets.c
+++ b/src/api/sockets.c
@@ -418,7 +418,7 @@ lwip_recvfrom(int s, void *mem, int len, unsigned int flags,
     ip_addr_debug_print(SOCKETS_DEBUG, addr);
     LWIP_DEBUGF(SOCKETS_DEBUG, (" port=%u len=%u\n", port, copylen));
   } else {
-#if SOCKETS_DEBUG > 0
+#if SOCKETS_DEBUG != 0
     addr = netbuf_fromaddr(buf);
     port = netbuf_fromport(buf);
 
@@ -1309,7 +1309,7 @@ int lwip_setsockopt (int s, int level, int optname, const void *optval, socklen_
       break;
     case TCP_KEEPALIVE:
       sock->conn->pcb.tcp->keepalive = (u32_t)(*(int*)optval);
-      LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_setsockopt(%d, IPPROTO_TCP, TCP_KEEPALIVE) -> %u\n", s, sock->conn->pcb.tcp->keepalive));
+      LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_setsockopt(%d, IPPROTO_TCP, TCP_KEEPALIVE) -> %lu\n", s, sock->conn->pcb.tcp->keepalive));
       break;
     }  /* switch */
     break;
diff --git a/src/core/ipv4/ip_frag.c b/src/core/ipv4/ip_frag.c
index bf219ebe..caa97a85 100644
--- a/src/core/ipv4/ip_frag.c
+++ b/src/core/ipv4/ip_frag.c
@@ -243,7 +243,7 @@ ip_reass(struct pbuf *p)
        variable. */
     LWIP_DEBUGF(IP_REASS_DEBUG,
      ("ip_reass: memcpy from %p (%d) to %p, %d bytes\n",
-      &ip_reassbuf[i], i, q->payload,
+      (void *)&ip_reassbuf[i], i, q->payload,
       q->len > ip_reasslen - i ? ip_reasslen - i : q->len));
     memcpy(q->payload, &ip_reassbuf[i],
     q->len > ip_reasslen - i ? ip_reasslen - i : q->len);
diff --git a/src/core/pbuf.c b/src/core/pbuf.c
index 7cf22c98..a5749e0b 100644
--- a/src/core/pbuf.c
+++ b/src/core/pbuf.c
@@ -482,8 +482,8 @@ pbuf_header(struct pbuf *p, s16_t header_size_increment)
     /* boundary check fails? */
     if ((u8_t *)p->payload < (u8_t *)p + sizeof(struct pbuf)) {
       LWIP_DEBUGF( PBUF_DEBUG | 2, ("pbuf_header: failed as %p < %p (not enough space for new header size)\n",
-        (u8_t *)p->payload,
-        (u8_t *)p + sizeof(struct pbuf)) );\
+        (void *)p->payload,
+        (void *)(p + 1)));\
       /* restore old payload pointer */
       p->payload = payload;
       /* bail out unsuccesfully */
@@ -750,9 +750,11 @@ pbuf_queue(struct pbuf *p, struct pbuf *n)
   p->next = n;
   /* n is now referenced to by the (packet p in the) queue */
   pbuf_ref(n);
+#if PBUF_DEBUG
   LWIP_DEBUGF(PBUF_DEBUG | DBG_FRESH | 2,
     ("pbuf_queue: newly queued packet %p sits after packet %p in queue %p\n",
     (void *)n, (void *)p, (void *)q));
+#endif
 }
 
 /**
diff --git a/src/core/tcp_out.c b/src/core/tcp_out.c
index a356fc21..bea45dee 100644
--- a/src/core/tcp_out.c
+++ b/src/core/tcp_out.c
@@ -605,7 +605,7 @@ tcp_keepalive(struct tcp_pcb *pcb)
                            ip4_addr1(&pcb->remote_ip), ip4_addr2(&pcb->remote_ip),
                            ip4_addr3(&pcb->remote_ip), ip4_addr4(&pcb->remote_ip)));
 
-   LWIP_DEBUGF(TCP_DEBUG, ("tcp_keepalive: tcp_ticks %ld   pcb->tmr %ld  pcb->keep_cnt %ld\n", tcp_ticks, pcb->tmr, pcb->keep_cnt));
+   LWIP_DEBUGF(TCP_DEBUG, ("tcp_keepalive: tcp_ticks %lu   pcb->tmr %lu  pcb->keep_cnt %u\n", tcp_ticks, pcb->tmr, pcb->keep_cnt));
    
    p = pbuf_alloc(PBUF_IP, TCP_HLEN, PBUF_RAM);